IPA: /ˌɪn.kənˈsɪd.ər.ɪt/
KK: /ɪnˈkɒnsɪdərɪt/
Not thinking about the feelings or needs of other people; showing a lack of thoughtfulness.
It was inconsiderate of him to interrupt her while she was speaking.
Inconsiderate → It is formed from "in-" (meaning not) and "considerare" (meaning to consider). The word describes someone who does not take others into account or fails to consider their feelings or needs.
Think of someone who is 'not' ('in-') 'considering' ('considerare') others — that's why inconsiderate means not being thoughtful of others.